Secretary of state Hillary Clinton and health secretary Kathleen Sibelius apologised to the people of Guatemala, and described the actions as 'clearly unethical'. Photograph: Rodrigo Abd/AP

The US today apologised for "outrageous and abhorrent" experiments in Guatemala by American doctors who infected hundreds of prisoners, soldiers and mental patients with syphilis in the 1940s.

The experiments were intended to test the use of penicillin, then an early antibiotic. Medical researchers sought out prostitutes with syphilis to deliberately pass on the sexually transmitted disease to men through intercourse. Other men were injected. Conducted between 1946 and 1948, the experiments were led by John Cutler, a US health service physician who would later be part of the notorious Tuskegee syphilis study in Alabama in the 1960s.

According to Susan Reverby, a Wellesley College professor who uncovered records of the experiment and thereby led to today's apology, Cutler chose Guatemala because he would not have been permitted to do the experiments in the US.

The researchers were interested in whether penicillin could prevent, not just cure, early syphilis infection.

"Cutler and the other physicians chose men in the Guatemala national penitentiary, then in an army barracks, and men and women in the national mental health hospital for a total of 696 subjects.

"Permissions were gained from the authorities but not from individuals, not an uncommon practice at the time, and supplies were offered to the institutions in exchange for access," Reverby wrote in a research paper.

"The doctors used prostitutes with the disease to pass it to the prisoners (since sexual visits were allowed by law in Guatemalan prisons) and then did direct inoculations made from syphilis bacteria poured onto the men's penises or on forearms and faces that were slightly abraded when the 'normal exposure' produced little disease, or in a few cases through spinal punctures."

Reverby said that the men were given penicillin after they had contracted the disease but it is not clear whether they were cured, and "not everyone received what was even then considered adequate treatment".

The US apologised in a joint statement by the secretary of state, Hillary Clinton, and the health secretary, Kathleen Sebelius, in which they described the experiments as "clearly unethical".

"Although these events occurred more than 64 years ago, we are outraged that such reprehensible research could have occurred under the guise of public health. We deeply regret that it happened, and we apologise to all the individuals who were affected by such abhorrent research practices. The conduct exhibited during the study does not represent the values of the US, or our commitment to human dignity and great respect for the people of Guatemala."

Guatemala said it would study whether there were grounds to take the case to an international court. "President Alvaro Colom considers these experiments crimes against humanity and Guatemala reserves the right to denounce them in an international court," said a government statement, which announced a commission to investigate.

Guatemalan rights activists called for the victims' families to be compensated, but a US official said it was not clear there would be any compensation.

The revelations have echoes of the Tuskegee study, in which over four decades from the 1930s, hundreds of African American men were left untreated after having contracted syphilis.